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High Energy Physics - Phenomenology

Title:Can $X(5568)$ be a tetraquark state?

Abstract: Very recently, the D0 collaboration has reported the observation of a narrow
structure, $X(5568)$, in the decay process $X(5568)\to B^0_s\pi^\pm$ using the
10.4${\rm fb}^{-1}$ data of $p\bar p$ collision at $\sqrt s= 1.96$ TeV. This
structure is of great interest since it is the first hadronic state with four
different valence quark flavors, $b,s,u,d$. In this work, we investigate
tetraquarks with four different quark flavors. Based on the diquark-antidiquark
scheme, we study the spectroscopy of the tetraquarks with one heavy
bottom/charm quark and three light quarks. We find that the lowest-lying S-wave
state, a tetraquark with the flavor $[su][\bar b\bar d ]$ and the spin-parity
$J^P=0^+$, is about 150 MeV higher than the $X(5568)$. Further detailed
experimental and theoretical studies of the spectrum, production and decays of
tetraquark states with four different flavors in the future are severely needed
towards a better understanding its nature and the classification of hadron
exotic states.